Reactors are used in inverter circuits for power supplies for use in home electric appliances such as air conditioners, motor-driven vehicles such as hybrid vehicles and electric vehicles, solar photo-voltaic devices, and other applications. Reactors are used, for example, to remove high-frequency components from AC power and to suppress power supply ripple associated with rectification. When such reactors are mounted together with other parts on circuit boards with limited mount regions, a magnetic shield structure for forming a closed magnetic circuit is required so that reactors can be surface-mounted in a limited area with no magnetic influence on other parts adjacent thereto.
FIG. 25 shows one of such surface mountable reactors. This surface mountable reactor, which is disclosed in Patent Document 1, includes an air core coil 101 of a flat conductor wire, a case 105 with terminals, and a pair of magnetic cores 109 with an E-shaped cross-section. The magnetic core 109, which is in what is called the EP form, includes a middle leg portion 110, an outer leg portion 111, and a connecting portion 112 connecting them.
The case 105 with terminals includes a rectangular frame 118 formed with terminals 119; and wall portions 106 and 107. One wall portion 106 of the two wall portions 106 and 107 has an arc-shaped surface on the distal side from the frame 118, and the coil 101 is inserted from the opening 115 side into the space defined by the wall portions 106 and 107.
Each wall portion 107 has a hole 108 formed in a position corresponding to the air core 102 of the coil 101, and a tubular member 121 made of an insulating material is inserted into the air core 102 of the coil 101. The components are assembled in such a manner that the case 105 with terminals is sandwiched between the pair of magnetic cores 109, the middle leg portion 110 of each magnetic core 109 is inserted into the tubular member 121 from outside the wall portion 107 and inserted into the air core 102 of the coil 101, and the end faces of the middle and outer leg portions 110 and 111 of the magnetic cores 109 are brought into contact with one another. Each end portion of the coil 101 is extended from the opening 115 of the frame 118, bent to cover the terminal 119 of the frame 118, and soldered, so that a surface mountable reactor with a magnetic shield. structure is obtained.